The abundance of questions that I receive regarding the care of an inherited holiday cactus, or schlumbergera, attests to the popularity and longevity of this plant.
These plants are called holiday cactus because their habit is to bloom around the time of one of three holidays - Thanksgiving, Christmas or Easter. You can determine which holiday cactus you have by looking at its leaves. The Christmas cactus has rounded notches on the margins of the stem segments while the Thanksgiving cactus has pointed tooth-like notches on the margins. The Easter cactus has tooth-like marginal notches with tiny spines or hairs on the stem segments. Most schlumbergera that I have encountered are Thanksgiving cactus, even those that I have purchased during the Christmas holiday. This is because many plant growers will force their Thanksgiving cacti into bloom for Christmas.
Caring for these plants is simple regardless of which type you have.
Soil - Schlumbergera require well-drained soil. I suggest that using a potting soil designed for cactus and succulents. The best time to repot holiday cactus is in the spring after active growth resumes, but it can be done at any time if the plant appears to be suffering.
Light - When growing holiday cactus indoors, place it in bright but indirect light. Direct light and excessive heat will scorch the leaves and cause the flower buds to drop. If you move your plants outdoors for the summer keep them in full to partial shade.
Water - In spite of its appearance and common name, schlumbergera is not a cactus. When in bloom these plants should be watered about once a week or when the top half of the soil in the container becomes dry. Lack of water will cause the flower buds to drop. After the flowers fade stop watering the plant for about 6 weeks. This will allow the plant to rest. During the spring and summer keep the plant consistently moist. Root rot from over watering is a common problem with these plants.
Fertilizing - When new growth emerges in the spring, begin a fertilizing with an all-purpose houseplant food mixed at half strength. Continue to do this once a month until October.
Pruning - A plant that can potentially live to be more than 75 years old is sure to need an occasional haircut. The best time to do this is in June. Simply snip off the top 2 or 3 segments of each stem. This will make the plant bushier and promote flower development. You can then root these cuttings to make more plants.
Propagation - Just as you back up data on your computer you can create a back up of your holiday cactus by taking a cutting. This will ensure the continuation of the plant if the original dies. Just cut a stem at a segment, about 2 or 3 from the tip. Stick the cuttings in loose soil or vermiculite and water only lightly for the first couple of weeks so the plant does not rot. Once it establishes some roots, begin watering normally and you'll have lots of plants to give to your friends.
Re-bloom - Holiday cactus need either cool night temperatures (between 55 and 60 degrees for 6 weeks) or extended periods of darkness to set flower buds. If you cannot meet the temperature requirement simply give the plant 13 hours of total darkness each night for several weeks. This can be done by keeping the plant in a closet or covering it with a dark cloth. During this time stop fertilizing and reduce watering. Once the buds set, return the plant to normal light and resume watering.
Bud Drop - Many people wonder why buds will drop from their plants before the flowers open. This can be caused by excessive heat, too much light, cold drafts, over watering, under watering or a sudden change in light or temperature.